Dengue, caused by the dengue virus and transmitted through the bite of infected Aedes mosquitoes, particularly Aedes aegypti, is a highly significant mosquito-borne viral disease worldwide. It is prevalent in tropical and subtropical regions, primarily in urban and semi-urban areas.
Dengue has been a documented disease for centuries, with evidence suggesting its existence as far back as the 18th century. The first recorded epidemics occurred in the 1770s and 1780s in Asia, Africa, and North America. The term "dengue" originates from the Swahili phrase "Ka-dinga pepo," which means "cramp-like seizure caused by the evil spirit." In 1906, the role of Aedes mosquitoes in transmitting dengue was identified, and subsequent studies confirmed the presence of different serotypes of the dengue virus.
Dengue is endemic in over 100 countries, primarily in tropical and subtropical regions of Asia, the Americas, Africa, and the Pacific. Annually, an estimated 390 million dengue infections occur, with approximately 96 million displaying clinical symptoms. The number of reported cases has surged in recent decades, posing a global health concern.
The primary mode of dengue transmission is through the bite of infected Aedes mosquitoes. These mosquitoes thrive in urban and semi-urban areas, where they breed in standing water. Additionally, dengue can be transmitted through blood transfusions, organ transplants, or from mother to fetus during pregnancy.
Dengue affects people of all ages and genders, with individuals living in or traveling to dengue-endemic regions being at risk. However, severe forms of the disease are more likely to develop in children, infants, and pregnant women. Factors such as immune status and genetic predisposition can also influence susceptibility to severe dengue.
Several risk factors contribute to dengue transmission, including rapid urbanization, unplanned urban development, and inadequate sanitation, which promote the proliferation of Aedes mosquitoes. Climate change, resulting in warmer temperatures and increased rainfall, also facilitates mosquito breeding and subsequently higher transmission rates. International travel to dengue-endemic regions can introduce the virus to new areas, potentially triggering outbreaks. Challenges in vector control, such as insecticide resistance and ineffective measures, hinder efforts to control mosquito populations and prevent dengue transmission.
Dengue's impact varies across different regions, with the highest burden observed in Southeast Asia and the Western Pacific. Countries like India, Indonesia, Malaysia, and the Philippines report significant numbers of cases. Latin America and the Caribbean also experience high incidence rates. While dengue primarily affects people in urban and peri-urban areas with poor sanitation and limited access to reliable healthcare, outbreaks can occur in developed regions with efficient mosquito control due to the introduction of new virus serotypes.
Prevalence rates and affected demographics can vary within regions and countries, influenced by factors such as population density, climate, healthcare infrastructure, and socio-economic conditions.
In conclusion, dengue is a major global health concern with significant epidemiological implications. Its transmission by infected Aedes mosquitoes, combined with urbanization, climate change, and inadequate vector control, contribute to its widespread prevalence. Dengue affects people of all ages, with severe consequences for children, infants, and pregnant women. Understanding dengue's epidemiology is crucial for developing effective prevention and control strategies to mitigate its impact.

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Seasonal Patterns: The data from mainland China demonstrates a clear seasonal pattern in dengue cases, with higher numbers occurring during the summer months and lower numbers in the winter months. This pattern remains consistent throughout the recorded years.
Peak and Trough Periods: The highest number of dengue cases in mainland China are typically observed in July and August, constituting the peak period. During these months, the number of cases significantly exceeds that of other months. In contrast, the trough period occurs in the winter months, particularly January and February, when the number of cases reaches its lowest level.
Overall Trends: There has been a steady increase in the number of dengue cases in mainland China over the years, with some fluctuations year-to-year. From 2010 to 2012, cases increased gradually, followed by a sharp increase in 2013. Subsequently, the number of cases fluctuated from 2014 to 2017, with certain months experiencing relatively high peaks. From 2018 onwards, there has been a general decrease in the number of cases, although sporadic outbreaks still occur.
Discussion: The observed seasonal pattern aligns with the known behavior of dengue, a mosquito-borne disease. The warm and humid weather during the summer facilitates mosquito breeding, resulting in increased dengue transmission. The peak in July and August corresponds to the period of highest mosquito activity and human exposure to the disease.
The overall increasing trend in dengue cases from 2010 to 2013 in mainland China is a cause for concern. Various factors, such as climate changes, population movement, and urbanization, may contribute to this trend. Efforts to control and prevent dengue should prioritize mosquito control measures, public education, and timely detection and response to outbreaks.
It is important to acknowledge that the presented data reflects only reported cases, and there may be underreporting or differences in surveillance systems among different regions in mainland China. Therefore, caution must be exercised when interpreting the data, and further research and analysis are necessary to achieve a comprehensive understanding of the dengue situation in the country.